Fix ITE Cache to be more Rust-like

[mattxwang]

This PR:

• renames things to be more consistent:
  • the table trait is now called IteTable. Not all the implements are Lru (so I'm not sure if that made sense), and Ite is bound to the type
  • the BddApplyTable is now called the LruIteTable, since the previous name didn't indicate that it was Lru or operated on Ite
  • the AllTable is not called AllIteTable for consistency
• flattens the builder::cache hierarchy, so now it is builder::cache::IteTable, etc. (instead of builder::cache::ite_table::IteTable)
• renames new_default_order to new_with_linear_order to be more clear
• removes the concrete type constructors for RobddBuilder, since they can imply a different type than the actual parametrized type (ex, an RobddBuilder over AllIteTable could return an RobddBuilder over LruIteTable, which doesn't make sense)
• automatically instantiates the IteTable for the RobddBuilder using the Default trait instead of having it in the constructor, since that's what we do in all callsites anyways

I would have loved to then alias the IteTables over a BddPtr as some sort of BddIteTable, but unfortunately, trait aliases are unstable.